Respiratory Physiology - Respiration under stress and at the limit Flashcards

1
Q

Respiratory response to exercise

A

VO2 increases in linear relationship as work rate increases, until reach VO2 max where it plateaus

Ventilation also increases linearly until reach anaerobic threshold, where lactate increases and ventilation increases even more as chemoreceptors are stimulated

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2
Q

Additional physiological changes with exercise

A

Pulmonary artery, venous and capillary pressures rise

Recruitment and distention of capillaries

Pulmonary vascular resistance falls

Pulmonary diffusing capacity rises

Shifts of O2 dissociation curve

Systemic vascular resistance falls

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3
Q

Effect on barometric pressure and inspired PO2 with increasing altitude

A

Barometric pressure decreases with altitude

Inspired PO2 therefore also decreases

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4
Q

Effect of altitude on ventilation

A

Ventilation increases - demonstrated with alveolar gas equation

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5
Q

Acclimatisation to high altitude

A

pH of CSF and blood normalises over time by bicarbonate buffering

Polycythaemia

Shift of O2 dissociation curve

Increased capillary concentration in muscle

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6
Q

Capillary pressures in high altitude

A

Uneven hypoxic pulmonary vasoconstriction

Therefore some capillaries exposed to high pressures

Leads to pulmonary oedema

Reverse it by descending from altitude

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7
Q

The bends aka decompression sickness

A

Nitrogen dissolves into tissue (esp fat tissue) as dive deeper

As come back up, nitrogen comes out of tissue and creates bubbles

Bubbles cause pain in joint + disrupt blood flow + CNS disruption

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8
Q

Management of decompression sickness

A

Prevention:
- Slow ascent
- Helium mixed gases

Treatment:
- Hyperbaric chamber

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9
Q

Use of Helium mixed gases

A

Helium has lower density so reduced airway resistance

He less soluble than Nitrogen

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10
Q

Concentration of dissolved O2 in blood with hyperbaric therapy

A

Maintains oxygenation where these is low oxygen carrying capacity of blood - eg carbon monoxide poisoning

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11
Q

Physiological changes in space

A

Increased pulmonary capillary volume

Increased pulmonary diffusing capacity

Increased CO and SV

More uniform distribution of lung blood flow and ventilation

Residual volume reduced

Changes in the deposition of aerosol particles (less sedimentation)

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12
Q

Why does pulmonary capillary volume increase in space

A

No gravitational pooling of blood

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13
Q

Cause for more uniform distribution of lung blood flow and ventilation in space

A

No gravitational pooling of blood to lower lung zones or compression of lung parenchyma

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14
Q

Pulmonary function in microgravity (space)

A

O2 uptake and CO2 output unchanged

Alveolar PO2 and PCO2 unchanged

No significant impairment in lung function - resolve when return

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15
Q

Pressure rise rate with diving

A

Every 10m of descent, pressure increases by 1 atmosphere

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